10.3. Sampling Data

The population from which samples will be created:

> v = 1:10

Sample one value from a vector:

> sample(v, 1)
[1] 9
> sample(v, 1)
[1] 1
> sample(v, 1)
[1] 2
> sample(v, 1)
[1] 9

Sampling multiple values without replacement:

> sample(v, 4)
[1]  1  7 10  3
> sample(v, 4)
[1]  6 10  5  3
> sample(v, 4)
[1] 10  4  1  9
> sample(v, 4)
[1] 5 2 4 3

Sampling all values without replacement:

> sample(v)
 [1]  8 10  3  5  2  7  4  9  1  6
> sample(v)
 [1]  6  7  1 10  4  5  3  9  2  8

This is essentially a random permutation of the original vector.

Sampling with replacement:

> sample(v, replace=TRUE)
 [1]  5  1  5  5  3  7  9 10  5  6
> sample(v, replace=TRUE)
 [1]  4  3 10  9 10  9  6  8  6  3

Notice that some values are repeating and some values are missing.

We can sample as many values as we want with replacement:

> sample(v, 20, replace=TRUE)
 [1]  8  6  1  8  7 10  4  4  2  2  9  5  9  7  7  6  1  3  9  6